The kingdom of heaven, the divine government, is founded on the fact of divine sovereignty--God is spirit. Since God is spirit, this kingdom is spiritual. The kingdom of heaven is neither material nor merely intellectual; it is a spiritual relationship between God and man.
If different religions recognize the spirit sovereignty of God the Father, then will all such religions remain at peace. Only when one religion assumes that it is in some way superior to all others, and that it possesses exclusive authority over other religions, will such a religion presume to be intolerant of other religions or dare to persecute other religious believers.
Religious peace--brotherhood--can never exist unless all religions are willing to completely divest themselves of all ecclesiastical authority and fully surrender all concept of spiritual sovereignty. God alone is spirit sovereign.
You cannot have equality among religions (religious liberty) without having religious wars unless all religions consent to the transfer of all religious sovereignty to some superhuman level, to God himself.
The kingdom of heaven in the hearts of men will create religious unity (not necessarily uniformity) because any and all religious groups composed of such religious believers will be free from all notions of ecclesiastical authority--religious sovereignty.
God is spirit, and God gives a fragment of his spirit self to dwell in the heart of man. Spiritually, all men are equal. The kingdom of heaven is free from castes, classes, social levels, and economic groups. You are all brethren.
But the moment you lose sight of the spirit sovereignty of God the Father, some one religion will begin to assert its superiority over other religions; and then, instead of peace on earth and good will among men, there will start dissensions, recriminations, even religious wars, at least wars among religionists.
Freewill beings who regard themselves as equals, unless they mutually acknowledge themselves as subject to some supersovereignty, some authority over and above themselves, sooner or later are tempted to try out their ability to gain power and authority over other persons and groups. The concept of equality never brings peace except in the mutual recognition of some overcontrolling influence of supersovereignty.
There can be no lasting religious peace on Urantia until all religious groups freely surrender all their notions of divine favor, chosen people, and religious sovereignty. Only when God the Father becomes supreme will men become religious brothers and live together in religious peace on earth.